Three dimensional display apparatus



April 11, 1961 M HlRsCH 2,979,561

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CASE

MAX HIRSCH ATTORNEY April ll, 1961 M HlRSCH 2,979,561

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0 INVENTOR. if; l I BY MAx HlRsoH j MMM TTRIVEX April ll, 1961 M. HlRscH2,979,561

THREE DIMENSIONAL DISPLAY APPARATUS Filed Nov. 12, 1958 10 Sheets-Sheetl0 INVENToR. MAX HIRSCH POIS/M6' muws M nited States Patent@ 2,979,561THREE DIMENSIONAL DISPLAY AAPPARATS VMax Hirsch, 4810 N.' 11th St.,Philadelphia 41,Pa.

Filed Nov. 12,' 1958, Ser. No.' 773,400

29 Claims. (Cl. 178-6.5)

This invention relates to an improved means for jpresenting images thatare reproductions in three dimensions of scenes, solid objects, andarrays of points in space. More particularly, this invention Vrelates toan improvement in the apparatus disclosed in my co-pending applicationfiled January 13, 1958, Serial Number 708,474, entitled ThreeDimensional Display Apparatus, and is a continuation in part thereof.

The representation of scenes 'by models, solid objects by sculpture, ofsurfaces by semi-relief sculpture, vandy of arrays of points in space bymechanicalmodels has been long known. The art of forming two dimensionalimages by photographic and electronic techniques has been well developedand this arthas been extended to lgive the perception of a thirddimensionV by means of stereoscopy. Attempts have been made togeneratetrue three dimensional images, for example, as taught in the FerrillPatent No. 2,361,390 and the Marx YPatent No: 2,543,793, wherebysections of a solid image are displayed von a screen. These patentsdisclose apparatus for displaying an image on a screen (or screenelements) which was cyclically moved with effective linear displacement.

This invention employs the principle of forming and displaying asequence of two dimensional images ofy sections of a solid on a screenwhich is Vrotated to sweep Vout a volume at such a rate that thepersistence of vision gives the perception of a sustained solid orthree'dimensional images, that may have color and motion. lFurthermore,in the preferred embodiment of this invention, the screen issubstantially parallel .to the axis of its rotation. The advantages ofthis arrangement are that the screen may be of such form thatconvenient'sectionsj(e.g. diametrical sections) of the solid can bedisplayed thereupon, large volumes can be swept out, and the forcescaused by the cyclic motion of the screen can be'made constant.. Anotherimportant aspect of thisv invention not found in the prior art is thatnew and superior means are provided for good definition of the displayedsolid image compatible with the short time available-.for the display ofsequential sections of the image comprising the entire solid. A devicefor displaying three dimensional views of solids or volumes may becalled a generescope, since the displacement of a series of twodimensional images generates solid or three dimensional'images.

The apparatus previously disclosed in one embodiment of my parentapplication, referred to above, employed a rotatable two dimensionalimage forming means which took the form of a single gun cathode raytube. Images formed on this rotatable cathode `ray tube were transmittedby a rotatable projection apparatus onto a screen rotating insynchronism with theprojection apparatus and the cathode ray tube. Oneof the improvements disclosed herein allows the cathode ray tube toremain physically stationary and provides electrical means for rotatingthe image formed on its face in synchronism with the movement of thescreen .and projection apparatus. In particular, there is disclosed inthis embodiment,

a computing means which forms a part of the three dimensional displayapparatus for automatically rotating the images on the face of thecathode ray tube'in synchronism with the rotation of the viewing screenand the means for projecting images from the face of the cathode raytube onto that screen.

In a second embodiment of this invention the need for a computing meansis obviated. Instead, a rotating magnetic deflection element is employedvto rotate `the images on the face of the cathode ray tube insynchronism with the viewing screen. Further, in both describedembodiments of this invention, the cathode ray'tube employed may have aplurality of electron guns to allow'for an increased rate of datapresentation.

The information or data signals for the three dimensionalimages mayoriginate in many ways such as a sensing means in the nature of a radardevice, direction'nders and generating means such as electroniccomputers and electrical function generators; but in any case the datasignals must be synchronous or made synchronous with the screen movementwhich displays the solid image. Further, the information may be derivedfrom a moving film source, as shall be disclosed in particular. .Byusing the time sharing Vtechniques and a plurality "of data sources,information of dierent content and from different sources may bedisplayed within a single 'three dimensional image to give an effectsimilar to 'superimposing in photography.

'The objects of this invention are many and those 'mentioned may beconsidered a typical category. One object'of this invention is toprovide 'an improved means yfor presenting three dimensionalpresentations.

Another object is to provide an improvedfmeansv'rfor displaying threedimensional images comprising fa rotating screen and image ,projectingapparatus,L and a stationary cathode ray tube.

Another object of this invention is to provideY animproved means fordisplaying three dimensional images comprising a rotatable viewingscreen .and image projection apparatus, a vstationary cathode ray tube,.and computing means for rotating the images on the face of thestationary cathode ray tube in synchronism with .the rotation of thescreen and projection apparatus.

Another object of this invention is to provide an improved means fordisplaying three dimensionalirnages comprising a rotatable viewingscreenand image projection apparatus, a stationary cathode'ray tube and arotating magnetic deection element therefor. f

Yet another object of this invention is to .providefan improved meansfor displaying images comprising a multiple-gun cathode ray tube.

Still another object of this invention is to provide a new and improvedmeans for displaying information comprising a cathode ray tube whereinthe data Adisplayed by said tube are determined by signals applied tothe deection elements of said tube.

Another object of this invention is to provide an apparatus fordisplaying images comprising anew and .improved moving film source ofdata and a transducer therefor. y Y

Another object of this invention is to provide a .new transducer havinga plurality of scanning elements and detection elements to be used inconjunction with a film storing data for converting said data intoelectrical signals.

Another object of this invention is to provide anew and improved displayapparatus for producing three dif to be expresslyunderstood, however,that the embodi- `ments of the invention disclosed herein are-meant tobe illustrative onlyv of vthe mechanisms vemploying the principles oftheinvention, and serve as a teaching of any equivalent elements that couldbe used in the described structures. Referringfnow to the drawings thatrforma partfof this disclosure, there is shown in:

Fig. l, a cross-sectional view of a multiple-electron gunr xed cathoderay'tube projection rotary type three di,-

mensional display assembly or generescope.

Fig. 1B, an isomerieview of the optical system. Fig. 2A, referencesvaxisvon the phosphor screen of the cathode ray tube when 61:0. f

Fig. 2B, same as Fig. 2A when 01:0-1-180". Figs. 3A and 3B, a blockdiagram of the crcuitsusedin conjunctionwith the apparatus of Fig. 1.

Fig. y4, a schematic diagram of the sense detect element.

Fig. 5, waveforms associated with the circuits of block diagram ofFig.3.

Fig. 6A, basic diagram of an angle comparator.

Fig. 6B, basic diagram of a height gate.

f Fig. 6C, basicfdiagramof a coincidence separator.

Fig.y 7, a block diagram of a height preampliiier. Fig. 8, waveforms ofvoltages inthe height preampliylier under different conditions.

Fig. 9A, representation of the mechanism of sin 0' potentiometermultiplier. f v f v f f f Fig. 9B, electrical diagram of ,sin 6'potentiometer multiplier.

Fig. 10A, top view of servo'motor, mechanical linkage,

and potentiometers.

Fig. 10B, side view of servo motor, mechanical linkage,

and potentiometers.y f f f Fig. ll, schematic representation of summingampliiier input circuit. f

Fig. l2, moving film record-signal producer.

Fig. 12A, top view of an optical transducer used with' apparatus of Fig.12.

Fig. 12B, front view of mask used in optical transducer. Fig. 13B,sectional view of a unied scene.

Fig. 13A, variable area record photographic film strip.

Fig. 14, sense waveforms and the number of the eld of the lm recordVentering the optical transducer.

Fig. l5, a sectional view of a multiple-electron-gun, fixed-cathode raytube, projection, rotary type three dimensional display assembly(generescope) employing rotary magnetic deflection means.

Fig. 16A, a top view of the base of the projection cathode ray tubeshowing the relative positions of its electron guns and theiralignment-rotation electrodes.

Fig. 16B, relative spot positions of electron beams on the face of theprojection cathode ray tube-no magnetic dellection-screen angle zero.

Fig. 16C, zonal swept areas on the face of the projection cathode raytube-screen angle zero.

Fig. 16D, same as Fig. 16B-screen angle forty-tive degrees.

Fig. 16E, same as Fig. 16C-screen angle forty-five de- Fig. 16F, same asFig. 16C-screen angle 180 degrees. Fig. 17, a block diagram of circuitsused in conjunction with the apparatus-of Figand Fig. 19.

Fig. 18, schematic diagram ofradius alignor circuit.

Fig. 19, moving lm reproducer-a cross sectional diagram.

Fig. 20, moving film transducer-a cross sectional diagram. t Y

Fig. 21A, a top view of the base of a ying spot scanner cathode ray tubeshowing the relative position of its electron guns and their aligningelectrodes.

Fig. 21B, zonal swept areas on the face of the ying spot scanner cathoderay tube-frame position, slightly below center.

Fig. 21C, broad view of film showing point positions and panoramasections on frames. f

lFig. 21D, front view of electron gun of image dissector tu e.

Referring now to Fig. l, there is shown a display apparatusv 50 forpresenting a three dimensional image to an observer comprising amultiple electron-guny cathode ray tube 51, lens 52, mirrors 53, y54,and 5S anda rear projection screen 56 arranged and mounted such thatelements 52 to 56 rotate together and that an image formed on the face51d of cathode ray tube 51 is prof jected onto'the rear projectionscreen S6. A central ray of lighty 68 emanating from a central point ofthe' face 51d of the cathode ray tube 51r illustrates thisy projection.The cathode raytube 51 is supported by an extended structure 203 thatgrips it over a considerable portion of its surface.' Cathode ray tube51 and struc ture 203v rest on stationary plate 204. This plate 204 isrigidly connected to the cylindrical housing member' 205 so that cathoderay tube 51 is rigidlyfiixed in position and does rnot rotate.Imagesformed on the cathode ray tube face 51d are rotated in unison withthe rotation of optical elements 52 to 56 by electrical methods to bedescribed. Cylinder 65 andstructure 79, ywhich support yoptical elements52 to 56, are rotated by a mechanism also to be described later. f f

Structure 79in its upper section consists of a periscoperlikearrangement on which mirrors 54 and 55' are mounted. The lower sectionof structure 79 supports mirror' 53 and lens 52 and contains an aperturefor the transmission of light from mirror 53 to mirror 54. The rearprojection screen 56 is mounted between the two aforementioned sectionsof structure 79. Cylinder and structure 79are supported by bearing 63,bearing 213, and constrained by rbearing 72. The assembly of supportstructure 79, hollow tube 65, yand the optical elements 52-56 rigidlyattached therein are driven by motor206 via gearing'arrangement (to bedescribed later) so that lens 52, mirrors 53,y 54, and 55, and screen 56all rotate in unison; whereas cathode ray tube 51 remains xed inposition. i

The basic supporting structure for the display apparatus 50 is the rigidhousing that consists of a long hollow cylinder 66a and shorter butbroader cylinder 66b connected by an annular plate 66e. A rigid arm 77attached to housing 66a has a fixed shaft 71 that fits into a bearing72. Bearing 72 keeps the rotating assembly of structure 79 and 65aligned with supporting arm 77 and cylinder 66a. While this rotatingsystem is not symmetrical, it can be balanced by well known methods.

The display chamber containing the rear projection screen 56 ispartially enclosed by transparent cover 57, through which the display onscreen 56 can be observed. The broad cylinder 66b and the annular ring66e enclose most of the remaining portion of the display chamber 70.

Chamber 70 can be made airtight. Thus, lens 52 is sealed withinstructure 79 and a rotary seal 64 is inverted between support member 79and structure 66a. Seal 73 which bonds transparent cover 57 to shaft 71completes the airtight enclosure. Seal 73 also serves an additionalfunction since it acts as a vibration insulator. A pneumatic exhaustpump 67 mounted on arm 77 and coupled to chamber 70 keeps the chamber 70at reduced air pressure, relieving the screen 56 and structure 79 of airloading, thereby lowering the drag on motor 206.

The apparatusfor rotating cylinder 65,1st1ucture 79, and elements 52 to56 comprise an electrical motor 206, which through shafts 207e and 207bat each end thereof, drives bevel gears 208a and 208]: respectively.Bevel gears 208a and 208b rotate bevel gears 209e and 209D respectively,which in turn drive their shafts 210a and 210b. Gears 211a and 211b arerigidly attached to their respective shafts 210a and 210b, and transmitthe motion they receive to ring gear 212 which is rigidly attached tocylinder 65. The double or balanced drive system {comprising-elements206 tV 2121inclnsive applies apure couple tothe ,dri-Ve -cylinder65.This 'obviates the 13P- plication of a balancing forceby bearing V213which supports and constrains cylinder v.65. The drive system is.basically supported 4by .the lowest-.housing member 20S, the base plate214 to wh-ich it is attachedl at its lower end, and the lower annularplate .-215 to --which it is `attached at its upper end. This plate 215is-attached-atritsfinner perimeter to hollow housing cylinder 66a.

Seal plate r216 3an annular ring, .together With;.--sea-l 217, seal 64,hollow yhousing 'cylinder 66a and rotating optical support cylinder 65form fan enclosure fior the major `mechanical friction.generating,-,elementsiofigenerescope; 5.0 such as gears#11m-.121111,.212, be aring '213, etc. T.Cathode ray tube ysupport,platc.;-204,rbasefplate 214, ,and .zt-.section ofthe-lowest housing-member 205 ferm an .enclosure for the motor 20.6;and the "lowerelements of the gear train, i.e., Vbevel Ygears 208:1, 208b, ,209m 209b,etc. Tubes 21Sa and -218b-enclose thje'rotating shafts 210a and 21tlbrespectively. f

An accurate ringgear 219 is rigidly mounted on rotating cylinder 65.Gear 219 drives a gear train`220 that .transmits the rotation ofcylinder l65 to servo generator 137 and is so proportioned that theangular V.displacements of the cylinder 65 and the armature (not shown).of the servo generator 137 areequal. Servo generator 137 controls servoamplier 243 which in turn drives servo motor 242 as shown in Fig. 3.Servo motor 242 is linked to and thus drives sine and cosinepotentiometers 66 and 61 respectively, also shown in Fig. 3. Thesepotentiometers 60 and 61 are each equipped with two rotatable arms sothat potentiometers -60 and 61 fur- -nish voltages which arerepresentative of plus and minus the sine and cosine of the angle(hereinafter designated of the cylinder 65 and consequently screen 56 atany instant.

Referring still to Fig. l, it can be seen that a spot of light producedon the screen 51d vof cathode ray tube 51 is projected onto the rearprojection screen 56 so that any position of the spot on the screen 51dof the cathode ray tube 51 has a unique corresponding position on therear projection screen 56 that is not affected by rotation. This is trueas all the optical elements 51-56 of the display apparatus (generescope)50 effectively maintain a tlxedspatial relationship with respect to eachother, since it will be shown that images on the face of cathode raytube 51 are electrically rotated in synchronism with lens 52, mirrors 53to 55 andscreen 56. When a spot of light shines continuously at a givenposition on the rear projection screen 56 and that screen is rotated atabout 2i) cycles per second or more, persistence of vision will ygivethe efect of a continuous circular ring of light whose center is on theaxis of rotation of the screen. When the spot is luminous only at agiven phase in the cycle of rotation and for a period that is a fractionof the cycle, the circular ring of light reduces to a circular segmentWhose length may be further reduced so that it effectively constitutes aspot of light in space. The position of the spot of light is uniquelydetermined by the phase, 0', in the cycle of rotation of the screen thatthe spot is luminous 'and its position on the rear projection screen 56,which `may be expressed as r, the radial distance perpendicular to theaxis of screen rotation and h', the distancealong the axis of screenrotation. The coordinates r', h, 0 are cylindrical and r', h' on therear projection screen are a projection of the usual (x, y) coordinateson the screen 51d of the cathode ray tube 51.

A given spot of light on the screen 51d of cathode ray tube 51, havingparticular coordinates (x, y) may be projected onto screen 56 so as tohave corresponding coordinates (r, h). This spot of light on screen 56may be seen from a wide angle in front of the screen. When -the opticalelements 52-56 are rotated 180 degrees mechanically and the image on thescreen 51d of cathode rayztube 51 isr.otated 180degrees .e1ectrica1ly,.aspot of 6 light mayfagain 11e-:projected on screen :562to `have the.samecoordinates (r', h), ifithenoriginal `vspot of -light on'the'screen 51d is electrically displaced so that it now has coordinates(-x, y). This second luminous spot on screen 56 has the same physicalposition as the first and may again be seen over a wide solid angle, but`this time from'a direction to the rear of theoriginal position :ofthescreenS. The .projected image on screen 56 of .1 a display xedfonVthe face of lcathode ray tube 51 is thus reverted, that-ffis,thehorizontal and only the horizontal (vx) Ycoordinate ofithe -image isreversed when screen 56 and iall.-.the;rrest of .optical elementsf52 to55 are rotated 180@deg-rees':mechanically:and the image on .the face ofcathode-ray tube 51.is.rotated l degrees electrically.

The electrical displacement of..a;.spot .of iight -onnthe screen 51d ofcathode ray tuberSlv from (x,..y.)-;to (-"x, y) effects a reversion, sothat the coordinatesfof thefldis'placed spotis (r, h) for'both-theoriginal posit-ion ofthescreen `5.6and its rotated .position 180 degreesremoved.

-every position upon which a spot of Alight may be 'projected in thevolume swept out'by the'screen 56 may Ybe seen, and consequently thepart of the structure 79 that supports mirrors 54 and55 Vdoesnot'elfectively obscure any'part of the whole displayed solid image. Itmay be noted that when the eye of the observer is'in the extension ofthesurface-of screen-56,v a luminous spot on the screen at that time is notdistinctly visible. However, since the observer may employ both eyes andmove his head, even this restriction may be minimized.

The position of points or aircraft in space may be simulated by variousgenerating means or they maybe sensed by radar, radiodirection finding,theodolite observation, etc. In any case, the data representing theattributes of point in space may bel presented as height above a givenlevel (h), distance along a given level from a given point (r), andangular bearing (0) with respect to some given origin. The threevariables r, h, and 0, or coordinates, uniquely determine the positionof a point in space. A corresponding spot of light of short durationprojected onto rotating screen 56 within 'display chamber 79 of thedisplay assembly 5t) shown in'Fig. l representative of the position ofthe aforementioned point in space, would have coordinates (r', h', 0'),where 0 is the angular value of the screen. Accordingly, the bearingangle of the spt of light, 0', r', and h' are the coordinates in thedisplay chamber 70 corresponding to the spacial coordinates 0, r, and hrespectively of a point in space.

To the three coordinates mentioned, a fourth (i) may be added whichidentities the target or indicates the value of some field (or somevariable quantity in space) such as brightness, potential, temperature,target size ata given position. Thus four variables (r, h, i, 0) can bepresented in the display system. While the description that followsexplicitly concerns itself with these four variables, a fth variable,time is implicitly involved. The displayed discrete spots can move andtheirmotion can be observed. And, therefore, the lifth variable, time isalso displayed.

Generescope 50 is similar in many Ways tothe trst generescope describedin my aforementioned parent application. As described there, twodimensional images formed on the face of a rotatable cathode ray tubeare projected onto a rear projection screen. However, in this invention,the cathode ray tube 51 and its deflection elements 235, 235', 239 and239 are fixed while the rear projection screen 56 rotates. In theearlier generescope, the cathode ray .tube .rotated with the .imagesformedon 7 its phosphor screen. In this invention, the image iseffectively rotated on phosphor screen 51d in unison with rearprojection screen 56 by computing the appropriate electrical signalsfrom data signals defining the position of image points.

As previously described, a point in space having coordinates (r, h, whenrepresented in the three dimensional display in display chamber 70 (Fig.l) has the coordinates (r, h', 6'). It may be seen from Fig. 1B that thecoordinates (r, h) are an optical projection of the coordinates (x, y)at all times if the reference frame X-Y on phosphor screen 51d rotatesin unison with rear projection screen 56. Refer to Fig. 2A showing thereference frames on phosphor screen 51d in detail. The convention isadopted that coordinates (x9, y0) refer to fixed reference frames X0--Y,the reference frame when 0'=0, and coordinates (x0, ya) refer torotating refer-` ence frame XYa. The deflection systems comprisingcathode ray tube elements 235 and 239 as well as 235' and 239' (Fig. l)produce deflections parallel to reference frames Xo-Yo. The coordinates(x0. y0) are computed from the coordinates (x6, ya) and the sine andcosine of 0', i.e., x0=x0 cos 0'-y sin 0' and Refer now to Figures 2A,2B, and 3. Each section, 240 or 240' of computer 199 accepts a pair ofdata signal corresponding to (x0, y0) when 0=6 and forms electricalsignals corresponding to (x0, yo) to effect rotation of an image point.When 0=0+180 degrees, each section 240 (or 240') again accepts thesignals corresponding to (x0, ya) but reverts them to signalscorresponding to (-x, ya) and then forms electrical signalscorresponding to (x'o, yo) from these reverted signals for the angle0=0l-l80. Fig. 2B shows the rotating reference frame at 0-|-180. The (xoyo) indicate that the coordinates are taken with respect to Xo-Yo axis:the primes indicate 0'=0-l180. This computation by computer 199 effectsreversion as well as rotation to satisfy the requirements previouslymentioned. A more detailed description of computer 199 is given below.

Refer again to Fig. 3 which shows a block diagram of an embodiment ofthis invention. The synchronous sampling circuits 49 comprising severalpoint channels 100 to 10021 supply data pulse signals to portion 245 ofarnplifiers 46 via one section 240 of computing circuit 199 for thedisplay in generescope 50 of a three dimensional array of discreteimages that represent points or objects in space.

Synchronous sampling circuits 49 require that ve sustained data voltagesbe supplied to each of the point channels 100 to 100n to represent thecoordinates or other attributes of each point or target to be exhibited.These sustained voltages are designated as follows;

(1) A voltage (RA) on line a, corresponding to the range, r, of thetarget.

(2) A voltage (HA) on line b, corresponding to the height, h, of thetarget.

(3) A voltage (IA) on line c, corresponding to the magnitude orrepresenting the identity of the target. (While only one such voltage isused here, several might be employed for more precise identification.)

(4) A voltage (E sin 0) on line d, proportional to the sine of thebearing angle of the target. A

(5) A voltage (E cos 0) on line e, proportional to the cosine of thebearing angle of the target.

The data voltages designated E sin 0 together represent unambiguouslythe bearing angle of the target.

The fve data voltages are sustained, that is, they vary only withattributes of the target they represent. These control voltages can becontinuous, or can vary in steps.

This set of five voltages may be derived from any sensing or generatingmeans such as radars, RF direction finders, sonar, computers, etc.

In my copending 8 application Serial No. 708,474 means for generatingsuch sets of five voltages by potentiometers were described.

The synchronous sampling circuits 49 convert the sustained voltageinputs RA, HA and IA into pulse signals RB, HB, and IB respectively,such that the amplitudes of the pulse outputs `are proportionalto theirsustained inputs and this conversion occurs repeatedly when 0'=0 and`0=0+l80. A description of the operation of synchronous samplingcircuits 49 is given below. The pulse signals RB and HB are fed into asection 240 of computing circuits 199 where the signals are manipulatedfor reversion [(xo, y0) to y(x.ty) when 0'=6|180] and for rotation[x0-:x9 cos 0'-y sin 0' and y0=y cos 0'Ix sin 0 when 6'=0 and again when0=0+l80 degrees]. The output pulses R0 and Hu, i.e. the computed signalsderived from RB and HB by section 240 of computer 199, are fed intosection 245 of driving amplifiers 46 along with identification pulse IBthat bypasses the computing circuits. The pulse signals R0, H0, anddelayed pulse signal IB are amplified and fed to deflection electrodes235, deliection electrodes 239, and intensifying grid 241 respectively(see Fig. l). Elements 235, 239, and 241 are members of one of theelectron guns of cathode ray tube 51.

Moving film source 149 supplies, via another section 240 of computingcircuit 199 and portion 245 of amplifiers 46, data representing aplurality of cross sections of scenes to generescope 50. These scenesare also displayed on screen 56. The data for source 149 may be storedon a transparent or transluscent film, intelligence being recordedthereon by the well known variable area technique. The two sources 49and 149 may be used independently or both may supply data to generescope50 for simultaneous display in the volume swept out by Screen 56.

The data on the film from source 149 is transmitted via a delay link 246and another portion 240 of computing circuit 199 synchronously with themovement of the screen 56. This synchronism is constantly maintained byan electro-mechanical linkage since motor 206 drives the rotary elementsof generescope 50 and controls the movement of the film in source 149through servo amplifier 243. By properly inserting the film in source149, a desired predetermined relationship between the data on the filmbeing detected by source 149 and the position of the screen isestablished. This relationship is such that when the screen is at anyangle, the data being detected by source 149 from the film therein isthe desired data to be displayed on screen 56.

The five voltages RA, HA, IA, E sin 0, and E cos 0 determining theposition of single points, such as an aircraft are transmitted via linesa to e to the radius matching circuit 80, height matching circuit 81,identity matching circuit S2, sine 0 matching circuit 83, and cos 0matching circuit 84, respectively, which are part of point channel 100of synchronous sampling circuits 49. The matching circuits to 84comprise amplifiers with suitable controls for determining their gain.While the following discussion deals with the display of a single point(representative of the position of an aircraft, etc.) by the circuitsshown at 100, it will be understood that all n point channels 100 to10011 operate in a similar manner for other points to be displayed, andmay be used to display any n points in space.

Radius matching circuit 80 is connected at its output to the input ofradius gate 90. Height matching circuit 81 and identity matching circuit82 are connected respectively to the inputs of height gate 89 andidentity gate 88. Sine and cosine matching circuits 83 and 84 eachtransmit their sustained sine and cosine voltages to both anglecomparators 85 and 85a. These angle comparators each receive anotherpair of sine and cosine signals from screen angle indicating sine andcosine potentiometers 60 and 61 respectively. When the screen angle isequal, or the reverse screen angle (the screen .gember @ofthefaforementioned gates'90., 89, and 88 via computing circuits 1199`and the set ofvampliiiers-49 :to the deection elements and control grid-respectiyclyvfof'one electron i,gun iucathode ray tube I51.Consequently, when` gates 910, 289, and 88.are conditioned, (i.e. -when0:0'), the

,cakth'ode ray`-tube 51 displays 1a spot of light that is projected ontoscreen 56, the position and intensity of which are thus determined bytheoriginal sustained volt- -ages (RA, HA, IA, Esinv0, E-rcos).

AAs .shallv be described, coincidenceseparator 95 sweeps the pointchannels 100 to 100,1, inconjunetion withhold muitivibrators `86 to 86nand ,metering .'pulsers 87 to-,87n.

These elements prevent pulse signals from ythe lseveral i point channels100 `to 10011 from interfering with each ,other `at the common drivingamplifiers 46 when any {several points have the samebearinglangle.v

A .fourth gate, the sense gate 255, forms sensepulses that indicatedirect (0:0) or yreverse (0=0'tl80) comparison. When 0:0 anglecomparator85 transmits ..a pulsetto sense multivibrator-254- Sensemultivibrator h.2;54'is a bistable device. The -pulse from anglecomparatorISS puts it into state numberone Thel output of sensemultivibrator 2 54 when in state one -is V1 and lis applied to one inputof sense gate 255. Whensense .gate 255 is conditioned along with gates88, 89, and 90 lzit; converts voltage Vlfinto a pulse signal,whoselamplitude v1 is proportional to V1. When 0=0{-180 reverse anglevcomparatorSSa Vtransmits ,aflpulse to sense multi- .vibrator 254putting it into state two. kIts output in state two is V2 .which is onehalf V1. The voltage V2 feeds into sense gate 255. When the gatesa88,89, 19;,0 and 255 `are conditioned again, sensegate -255 convertsvoltage V2.@into a pulsev signal whose amplitude isV v2ewhere-v2 is .onehalf v1. The pulse signals formed by `sense, gate -255 are synchronouswith pulse signals RB, HB, IB. When the output of gate 255 is equal tov1 it indicates 0=0, but when the amplitude is v2 it indicates 0'=0| Thepulse signals fromall .sensegates 255 to 255n feed into sense detect 252Vin channel 240 of com- -puter 199. The sense pulses as well as the.pulse signals r.are all negative as shall be explained.

The effect of any point channel 100 to 10011 is tosample three of thesustained data signals synchronously with ythe movement of the displayscreen 56. .It uses the re- -maining two sustained data signals (theangle signals) to yeifect proper synchronism. If the target pointchanges so as to change its bearing angle, the corresponding image spotalso changes its angle. `If this change is fairly large, e.g. or 20degrees `and occurs within the period of a single rotation of thescreen, the image .spot will not be continuously available to view.There are two solutions to this problem, the rateof rotation of th'escreen may be increased so that no large change of positionoccurs withina single cycle, or the data displayed may be limited to slower changes.Slow changes of position imply slow changes of data signals and hencesmall bandwidths. These will be D C. to low audio signals. This, ofcourse, applies to the other signals, RA, HA, ,and IA. The identitysignal, IA, might also be narrow band, but rapid variation in intensitymay be used as an Videntiication code and require somewhat largerbandwidths. v

The identification matching circuit 82 is adjusted so ythat the voltagesat the output ultimately determine `the brightness of the spot of lighton the face of the cathiode Yray tubefSl fbymodulating a control grid241ojf the cathode ray tubeg51. Ithefsine 0,and cosine @matching vcircuits83v and l84are adjusted so that the maximum voltages attheiroutputs aremade equal to the maximum voltages from the s creeniangle indicatingsine potentiometer 60 and cosine potentiometer 61 respectively. Themaximum output voltages of matching circuits 83 and 84 shall hereinafterbe designated as voltages E1 and E3 respectively, and the maximumvoltages from potentiometers A60 rand 61 shall be designated as voltagesE2 and E4 respectively. Thus, the voltages are adjusted so that E1=E2and E3=E,2. As previously mentioned, sine and cosine potentiometers 60and 61 produce voltages which are the sine and cosine of the bearingangle of the screen 56. It will beappreciated that each potentiometermaybe provided with two wiping arms so that .two voltages are produced,wherein one voltage is proportional -to the vgiven yfunction of thescreen r56 bearing angle, and the other voltage is proportional to minusthe ,given function of that angle.

Accordingly, the outputs from elements 60, 61, 83, land 84 -shall rbereferred -to as indicated in the following chart:

Element: Output voltage Matching circuit 83 E1 sin 0 Matching circuit84, E3 cos 0 lSine potentiometer@ E2 sin 0'; --E2 sin 0' Cosinepotentiometer 61 E4 cos 0'; E4 cos 0' where 0=bearing of the target and0=angle of the screen '56. t

AFour voltages Elsin 0;,E2 sin 0'; E3 cos 0; and E4 cos 0', the waveforms of which are shown in Figs. 5A and 5B, are fed into anglecomparator 85.

Figure 6A illustrates the angle comparator 85 and it operates so `as toyield an output pulsewhen the bearingangle of the ytarget and theangular position ofthe 4screen are equal, i.e., when E1 sin 0v-E2 sin 0and E3' cos 0=E4 cos 0 indicating that 0:0. The cathode follower buffersy85b and 85e (Fig. 6A) receive the voltages El sin 0 and E2 sin-0respectively and feed them into sine wave comparator 85f. The buffers85h and 85C show the same constant output impence to the sine wavecomparator 851 and serve to prevent comparator 851 loading fromdisturbing the input signals that also go to other circuits. The sinewave comparator 85j is a form lof the comparators to produce a markerwhen a sinusoid equals a iixed voltage (reference-waveforms by VChanceet al., p 348 et seq., first ed. 1949). The sinusoid is E2 sin 0 (Fig.5A) that varies at about 25 cycles vper-second, and E1 sin 0 (Fig. 5A)is taken as the iixed voltage. This voltage E1 sin 0 is of course notfixed in the absolute sense. It may have all values between -t-El and-E1, and it may vary with time, but its time yrate of change aspreviously described is very slow compared to E2 sin 0. Therefore, itmay be taken as a reference kor iixed voltage. These two voltages, E1sin 0 and E2 sin 0', have the some value twice per cycle, e.g., atpoints a and al and again a2, a3 (see Fig. 5A). The sine Vwavecomparator 85]c (Fig. 6A) produces a positive marker pulse wheneverthese two volt-y ages are equal. Fig. 5C shows such markers at C0, C1,C2, C3. These marker pulses are impressed upon the first Ycontrol grid85h of a dual grid control tube 85j, such as the 6AS6, which serves as acoincidence detector.

The cathode follower buffers 85d and 85e (Fig. 6A) function for thevoltages E3 cos 0 and E4 cos 0 in the same manner as buffers 85h and 85Cdo. The sine wave comparator 85g also functions in the same way as itsanalog comparator 851. Thus, when its two voltage inputs are equal, asshown in Fig. 3B at b1 and b2, and again b3 and b4, this comparator 85galso produces -positive marker pulses. `These are shown at d1, 12,d3,`andd 11 in Fig. 5D and are impressed upon the second control grid851' of the coincidence detector, 851.

When and only when marker pulses from both cornparators 85]c and 85g aresimultaneously impressed upon both control grids 85h and 85 does thecoincidence detector 85j conduct and a pulse formed at its output. Thedetector output pulses e1 and e3 shown in Fig. 5E indicate coincidenceof pulses c1 and d1 along with c3 and d3 respectively. When pulse c1 isproduced El sin =E2 sin 0', and when pulse d1 is produced E3 cos :E4 cos6. Accordingly, the pulse e indicates that the aforementioned twovoltages are equal and 0:0. This holds as E1=E2 and E3=E4 by theadjustment of the sine and cosine matching circuits 83 and 84respectively as previously described.

The reverse angle comparator 85a (Fig. 3) has the same physicalstructure as angle comparator 85, but operates so as to yield an outputpulse when the bearing angle of the target is equal to the reverse angleof the screen, i.e., 6==9l80. This holds when E1 sin 0=E2 sin 0' and E3cos 0=E4 cos 0. The voltages E1 sin 0 and -Ez sin 0 the waveforms ofwhich are shown in Fig. 5F are compared within reverse angle comparator85a to produce marker pulses when they are equal. These marker pulsesare also produced as pairs per cycle at f1 and f2, and again at f3 andf4 (see Fig. 5F). The voltages E3 cos 9 and E4 cos 9' the waveforms ofwhich are shown in Fig. G are also compared within unit 85a to producemarker pulses when they are equal. These voltages E3 cos 0 and E4 cos 0are equal at g1, g2, g3, and g4. There is coincidence at f2, g2, and atf4, g4 to produce coincidence pulses at h2 and h4 respectively as shownin Fig. 5H. The coincidence output pulses h2, h4 occur only when9=6-l80, and are the output pulses of reverse angle comparator 85a.

Angle comparator 85 and reverse angle comparator 85a (Fig. 3) are bothconnected at their outputs through isolating buffer 86a to an input ofhold multivibrator 86 which is a bistable circuit. An output signal fromeither angle comparator 85 or 85a causes the hold multivibrator 86 tochange its state from state one to state two. The other input of holdmultivibrator 86 is connected to the output of coincidence separator 95(to be later described in connection with Fig. 6C). Hold multivibrator86 is caused to change back to its first state by a pulse fromsepa-rator 95 within such a short period after having received its firstpulse from either comparators 85 or 85a that angular definition is notsubstantially reduced by the movement of screen 56 within that shortperiod, as shall be shown. The output of hold multivibrator 86 isconnected to the input of metering pulse generator 87 which is amonostable multivibrator, so that when hold multivibrator 86 revertsback to its lirst state, it triggers metering pulse generator 87, whichin turn produces a metering pulse of fixed amplitude and fixed duration.The output of pulse generator 87 is connected to a second input of thegates 88, 89, 90 and 255, and consequently each of these aforementionedgates are alerted for a period equal to the duration of the meteringpulse. The first inputs to the gates 90, 89, and 88 are, as previouslymentioned, connected to the output of radius matching circuit 80, heightmatching circuit 81, and identification matching circuit 82respectively; and therefore, when radius gate 90, intensity gate 88, andheight gate 89, each receive an activating pulse from metering pulsegenerator 87, they produce pulse data signals, the amplitudes of whichare proportional to the sustained voltages at their tirst inputs.

Reference is now made to Fig. 6B in conjunction with Fig. 3 illustratingin more detail the height gate 89, which may be considered typical ofthe gates 88, 89, 90, and 255. Fundamentally, the height gate includes adual control electrode tube 891, such as the 6AS6. The iirst controlgrid 89h receives a sustained data signal, here the adjusted heightsignal from the height matching circuit amplitude is made proportionalto the sustained adjusted input signal. The output signal pulse taken atthe anode 89d is always negative permitting the isolating diode 89econnected thereto to act as a switch. When a negative signal pulse isgenerated at anode 89d, diode 89e acts as a short and the pulse passesto the common input of height preamplifier 248 in channel 240 ofcomputer 199.

When, however, no signal pulse is generated and tube 89b is quiescent,diode 89e` acts as an open circuit. Consequently, the driving impedanceof tube 89b is prevented from loading down any height output pulsesignals from other height gates up to and including 89u (Fig. 3), sinceall the height gates are in para11el.

Referring again to Fig. 3, identity gate 88 is connected at its outputthrough delay element 246 and intensifier driving amplier 253 to thecontrol electrode 241 of cathode ray tube 51. Thus, the signal from gate88 determines the brightness of the spot produced on the screen 51d ofcathode ray tube 51 and consequently on viewing screen 56. Height gate89 is connected via height preamplifier 248 and channel 240 of computer199 to the deflection elements of one electron gun of cathode ray tube51, and hence the signal formed by gate 89 in part determines theposition of a spot of light on viewing screen 56. Radius gate 90 isconnected via radius preamplifier 244 in channel 240 of computer 199 tothe deflection elements of the same electron gun of cathode ray tube 51and the signal formed by gate 90 also in part determines the position ofthe spot of light on viewing screen 56. Sense gate 255 is connected tosense detect 252 of channel 240 of computer 199 to indicate direct(0'=0) or reverse (0=6|l80) comparison. Thus, when 0:0 'and again when0=0'180, the angle comparators 85 and 85a respectively trigger thedisplay of a spot image by causing the metering pulser 87 to activatethe radius gate 90, height gate 89, identity gate 88, and sense gate255.

As previously stated the coincidence separator sweeps the point channelsto 100n in conjunction with the hold multivibrators 86 to 8611 andmetering pulser 87 to 8711. This action prevents pulse signals from theseveral point channels 100 to 100n from interfering with each other atthe common driving amplifiers 46 when any several points have the samebearing angle. It was also stated that hold multivibrator 86 is causedto change back to its first state by a pulse from coincidence separator95 within such a short period after having received its first pulse fromeither angle comparator 85 or 85a that angular definition of the displayis not effectively' reduced by the movement of screen 56 within thatperiod. The sweeping action of separator 95 consists in repeatedlysending a pulse to each of the hold multivibrators 86 to 8611 intemporal sequence; the repetition period of the pulse received by eachhold multivibrator 86 from separator 95 is of short duration as comparedwith the time it takes the screen 56l to sweep an angle corresponding toA0', the angular definition.

It can be stated that 0=21rft, where i equals the frequency of therotation of screen 56 and A0'= the angular definition where A0=21rfq,and q the period corresponding to the angular definition, i.e., thedefinition interval. Therefore, if f=i25 c.p.s. and A0=1` degree; q=$5$60=111 microseconds. If there were u point channels whose points couldall possibly have the same bearing angle, the signal pulses from thegate circuits each -hold multivribator 86from coincidence separator thusbeen established as equal to or less vthan .q. l Referring now to Fig.l6C in conjunction with Fig; r3, Yitmay vb elseen that coincidenceseparator 95 comprises a frequency reference which includes a stableoscillator `llilqwllose` frequency yis n/q. Oscillator 131 transmits itssignals to spike generator 132. Spike generator 132 consists ofacircuitsuch as va-multiar, ythat converts its sinusoidal input intoasharp pulse output `at a fixed phase ofthe input. -A representation ofthese spike signals is shown 4in Fig. 51. The spike period is of courseq/n. The spikesignal is fed in to ring counter 133 that comprises a ringof bistable. elements 134 to 134:1. All the bistable elemente-13,4 .to13,4n receive the spike signals and all the bistable elements, exceptone, are in the same state, here called -passive or non-conducting. Thisone exception is inthe rother state, here called active or conducting.Any element, for example, 134i, changes its state from passive to activeonly when it receives both a spike signal and a permissor signal from animmediately preceding active eilementgeg. 134 (yl-I). This action causesthe preceding active `element 1-34 (i-I) also to change its state topas-v sive. l`Thus, only one element is changed to an active stateincyclic ysequence each time a spike pulse is received from spikegenerator 132. Each of these bistable elements 134-to 134n generates apulse when it is switched to'.y its active state, .which is-transmittedto corresponding hold-multivbratorsr87 to y8711 respectively to whichelements 134 to 134n are.` connected. Thus spike numbered :triggerselement 134, .and element 134 in turn sends 2 a pulse to holdmultivibrator 87. Then, spike numbered 1 `triggers elementl134a, andelement 134 in turn sends arpulse to hold multivibrator in point channel100a (not shown). Thisproceeds until spike numbered n triggers element134n whereupon hold multivibrator 87n is sent a pulse. The next ypulseis number 0 again and the cycle repeats continuously.

'Thevsignal pulses formed by the gates 88, 89, 90 and 255 (Fig. 3) havea duration equal to that of the metering pulse received from meteringpulse generator 87. To prevent interference, the metering pulse durationis made equal to L such that L is equal to or less than q/n. This pulse`L is shown in Fig. J. Thus, signal pulses from the gates 188,189, v90,and 255 also have a duration L, and this .-is alsofapproximately theperiod for which electrons inV cathoderay tube51 illuminate the phosphorscreen '51d on the face of the tube 51p. The period for which light isemitted by 4cathode ray tube 51 is equal to L-i-D; Where D is the decaytime of the phosphor (see Fig. 5K). A fast phosphor is used whose decaytime D is equal or less than the definition interval minus the elec-*tron illumination period (D=q-L).

To avoid jitter of the spot within the definition intervalg 4and thus-within the angular definition A0', the frequency reference 131.(Fig.6C) may be synchronized by a .sine .signal e.g E2 vsin 0 fr om sinepotentiometer 60 (Eig. 3).

While the coincidence separator 95 operates on all point channels 100 to100n in the system of Fig. 3, this is notthe only mode of operationpossible. Where the data precludes the possibility of some groups ofpoints having the,:same-bearing angle, the coincidence separator 95 mayAsweep such groups *of point channels in parallel.

The previously described computations corresponding to vreversion(changing (x9, ys) to (-x, yg) when 0=0-} 180) and computationscorresponding to rotation (i.e. x0,=x cos y0'-y sin 0 and y0=yo cos 0lxsin 0') are made by each channel 240 and 240 of rotation cornputer A199yshown in Fig. 3 to which reference is kagain made. The description ofchannel 240 givenbelowfap- `plies withA lsome slight changes'also tochannel 240'.

When the vbearing angle of a point, P, to be displayed is equal to theangle of screen 56 (when 0:0), the gates 88, 89, 90 and 255 operate andconvert -their input Yvolt- `tages to pulsek signals for identity,height, radiusfand sense respectively. `The radius pulse signal RB fromgate Y `is fed into radius preamplifier 244; the height -pulse signal HBfrom gate 89 is fed into height preamplifier 248; and the sense pulsesignal, v1, is fed from gate 255 to sense Vdetect 252. The identitypulse signal vIB yfrom gate 88 bypasses the computer'199 andfis fedlinto identity driving amplifier 252. To improve the coincidence ofidentity pulses IB with computed radius andr height pulses fed intodriving amplifiers 46, delay line 246 having a short delay period (afraction of a microsecond) may be introduced before the identity drivingamplifier 252.

The sensedetect 252 has three outputs, A connected to direct gate 249,Bconnected to reverse gate Y25), and C connected to both radiuspreamplifier 244 and height preamplifier "248. As previously describedall sense gates 255y to 255n feed negative sense pulses into sensedetect 252. Whenthe amplitude of a pulse from any of the Agates'255 toy25511 is v1, it indicates 0=0 and when the amplitude of a pulse is v2,it indicates 0'=0-}-l80. Also v1=2v2.. Refer now to Fig. 4 whichillustrates the operation of sense detect 252. The sense detect 252cornprises a diode 256 connected at its cathode to the outputofvgate'255 in all the point channels 100 to 100n. The anode of dode 256is connected through a resistance network to a potential of -i-VZ volts.Additionally, the anode of diode 256 is connected to the input ofamplifier 257, having a gain of G0. The output of amplifier 257 isconnected to terminal A (i.e. the input of gate 249) and to one input ofsumming amplifier 259'via amplifier V258. The outputs of gates 255 arealso connected to the input of amplifier 260 which also has a gain ofG0. Amplifier 260 is in turn connected at its output to the second inputof summing amplifier 259. The output -of amplifier 259 is designated asoutput B and is connected to the input of reverse gate'250. Theamplifier 260 is also coupled to output C and thence to preamplifiers244 and 248 via cathode follower 261. Output C is clamped via diode 262and a voltage divider to an upper potential of -i-Vc volts.

When the pulse received byv sense detect 252 is .v1 it passes throughdiode 256 whose anode is set at a fixed potential, v2, where v1==2v2.Thus, only that portion of the pulse more negative than {v2} passesthrough diode 256. The amplitude of the transmitted pulse is v1-v2.Since, as previously explained, v1=2v2 then v1-v2=v2. This reducedpulse, v2, is amplified by gain G0 of amplifier 257 to a positiveamplitude of Govz and passes out through terminal A of the sense detect252 to direct gate 249 where it operates as a positive permissor pulse.The output Govz of amplifier 257 is amplified again by arnplifier 258 toa negative pulse of twice the input amplitude, or G01/1 and thenimpressed on one input of summing amplifier 259. Meanwhile, the originalinput pulse v1 applied to the cathode of diode 256 has passed throughamplifier 260, Whose gain is also G0 where it is made a positive voltageGovl, and then impressed on the other input of summing amplifier 259.Since the inputs are equal and opposite in polarity, they cancel and theoutput of summing amplifier 259 is zero. The output of amplifier 259 isconnected through terminal B to reverse gate 250, and the quiescentoutput of amplifier 259 is negative, and acts as an inhibitor on reversegate 250.

When the pulse received by sense detect 252 has an amplitude v2', itcannot pass through diode 256 so the output of amplifier 257 remainsquiescent. The quiescent negative voltage output of amplifier 257 actsas an yinhibitor on direct gate 249 through terminal A. However, theoriginal negative pulse v2 is amplified by gain Gb of 'input to summingamplifier 259 from amplifier 258 is zero. This positive pulse Govz isthen impressed through terminal B on reverse gate 250 where it acts as apermissor pulse. When no sense signals are impressed on sense detect252, both output terminal A and B are negative and inhibit both gates249 and 250.

In both cases when '=6 as well `as when 0'=H-|l80 the positive outputpulses from amplifier 260` which are Gov, and Govz respectivelyarepassed through a cathode follower 261 which functions as an isolator.The pulses leaving cathode follower 261 are limited by diode 262 to anamplitude of vc which is less than Govz. These limited pulses, or levelpulses, leave the sense detect 252 at terminal C and are transmitted topreamplifier 244 and height preamplifier 248.

The radius and height preamplifiers 244 and 248 (see Fig. 3) convert thenegative monopolar radius and height pulse signals, RB, HB, they receivefrom any radius gate 90 or height gate 89 respectively, into bipolarpulses, RC, HC. The radius preamplifier 244 transmits its bipolar radiuspulses Rc to both direct gate 249 and reverse gate 250. The heightpreamplifier 248 transmits its bipolar height pulses Hc to heightamplifier 229. The conversion to bipolar pulses is needed to makecomputer 199 operable for all four quadrants of cathode ray tube 51 (seeFig. 2) Le. so the electrical equivalents of positive and negativevalues of radius and height (x and y) are developed.

Refer to Fig. 7 showing a block diagram of the height preamplifier 248,and to Fig. 8 which shows a graph of the Vwave forms within heightpreamplifier 248 under dif- 'ferent conditions. The height preamplifier248 comprises a pair of cathod-e followers 263 and 264 which areconnected at their outputs to thel first and second inputs of a sumingamplifier 265 having a gain of G1. The output of summing amplifier 265and consequently the output of height preamplifier 248 is connected tothe input of height amplifier 229 (Fig. 3). Cathode followers 263 and264 are connected at their inputs to the outputs of gates 89 in pointchannels 100 to 10011 and to the output of sense detect 252,respectively.

A negative height signal pulse of amplitude vH (Fig. 8B) from heightgate 89 is fed into cathode follower 263. The positive sense pulse ofamplitude vc from terminal C of sense detect 252 is fed into cathodefollower 264. The two pulses add algebraically at the input of summingamplifier 265. Fig. 8A shows the sense pulse vc with a time base; Fig.8B shows signal height pulses with the same time base yfor threedifferent conditions, cases I, II, and III; Fig. 8C shows the algebraicsum pulses, vH-vc, at the input of summing amplifier 26S for threecases; and Fig. 8D shows the inverted output of summing amplifier 265(vH-vc)G1 for the same three cases. The voltage, vc, corresponds to aheight of zero on cathode ray tube 51 (Fig. l or 3). In ca'se I, apositive height is represented by a large negative pulse height signal,vH (Fig. SB-I). This pulse when added to a positive vc pulse produces anegative (vrp-vc) output (Fig. 8C-I). The output of summing amplifier265 is a positive (vH-vc) G1 pulse. A negative height on cathode raytube 51 is represented by `a small negative value of vH i.e. IvHl lvc incase II, Fig. 8B-II. The small negative voltage vH added to vc producesa positive (vc-vH) pulse shown at Fig. 8C-1I and a negative (vc-vH)G1 atthe output of summing amplifier 265 shown at Fig. 8D-II. A 4height oflevel zero (on the axis of cathode ray tube 51) is represented by avalue of vH such that fvHl=|vcl shown in Fig. SB-III. When thiscondition occurs a zero level is produced at both the input and outputof summing amplifier 265 shown respectively at Fig. 8C-III and Fig.8DIIL Thus, a positive or negative height electrice-l pulse signal Hc isfed from height preamplifier 245 Y1a such that its value corresponds inmagnitude and polarity to thevalue of the height (y) of the point, P,being represented on cathode ray tube 51 and consequently on the screen56,

The radius preamplifier 244 (Fig. 3) is similar to the heightpreamplifier 248 and converts the negative radius pulse signals, RB,into bipolar radius pulses RC that correspond to the radius positionalpolarity and magnitude (x) of the point, P, being represented on cathoderay tube 51. The bipolar output radius pulse is fed into both the directgate 249 and the reverse gate 250. When 0'=0 the direct gate 249 acts asa permissor and the reverse gate 250 acts as an inhibitor ion controlvoltages from sense detect 252 as previously described. Thus, thebipolar pulse, RC, passes through gate 249 andis applied to radiusamplifier 222 when 0:0. When 0=0I180, the direct gate 249 acts as aninhibitor and reverse gate 250 acts as a permissor again by controlvoltages from sense detect 252. The bipolar pulse, Rc, now passesthrough reverse gate 250 into inverting amplifier 251 where it isinverted to a RC pulse and applied to radius amplifier 222. Thus, when0=0l80, RC, is inverted but HC is not, so the electrical equivalent ofreversion is affected.

When reverse gate 250 is inhibited and direct gate 249 isropen (i.e.only when 9:0') then the radius amplifier 222 and height amplifier 229amplify bipolar pulse signals RC and HC. The radius signal R fromamplifier 222 is passed into inverting amplifier 225 where it isinverted to a --Rpulse. The height signal H is passed into invertingamplier 232 where it is inverted to a -H pulse.

The amplified radius signal R, which is a function of voltage RA is alsoapplied to the upper terminals of sin 0 potentiometer 223 and cos 0'potentiometer 224, as well as inverting amplifier 225. The invertedradius signal, -R, from amplifier 225 is fed into the lower terminals ofsin 0 potentiometer 223 and cos 0' potentiometer 224. The dotted line226 indicates a mechanical linkage that drives the wiper arms ofpotentiometers 223 and 224, as well as 230, 231, 223', 224', 230 and231' in unison with the screen movement 56.

Refer now to Figures 9A and 9B which show respectively a physical andschematic representation of potentiometer 223. The electrical signals Rand -R from amplifiers 222 and 225 are applied respectively to the upperterminal 227u and the lower terminal 2271 ofsine 9' potentiometer 223. Awiper arm 228 is rotated by a mechanical linkage 226 connected to motor242 (Fig. 10A) that turns the wiper arm 228 in unison with rearprojection screen 56. The angle l,of wiper arm 228 at any instant, isequal to the bearing angle of rear proiection screen 56, and the voltageoutput of the wiper arm 228 is f -R sin 0'. Therefore, there is aneffective multi- Aplication of the radius signal R and sin 0. The cos 0'potentiometer 224 operates in a similar manner except that its wipingarm is displaced degrees ahead, and its output is i-R cos 0'.

Referring back Ito Fig. 3, it will be appreciated that in a similar waya height signal, Hc, which is a function of voltage HA, is fed intoheight amplifier 229. The amplified signal, H, from element 229 isconducted to the lower terminals of sin 0 potentiometer 230, the upperterminal of cos 0 potentiometer 231, and an inverting amplifier 232. Theinverted height signal, -H, from amplifier 232 is applied to the upperterminal of sin 6' potentiometer 230 and the lower terminal of cos 0potentiometer 231. These potentiometers 230 and 231 function in the sameway as potentiometer 223, but since the inputs of potentiometer 230 havebeen inverted (as compared with the inputs of potentiometer 223) itsoutputs are respectively -H sin 0 and -l-H cos 0. The outputs ofpotentiometer 224 and 230, R cos 0' and -H sin 0', are fed into radiussumming amplifier 233. The two signals are added algebraically andamplified here. The output of summing amplifier 233 is R cos 0' -H sin9' and is equal to R0 where -Ro corresponds to x0, R to x0, H to y, inthe expression x0=x0 cos Vn-y0 sin 0 previously ses -17 forth. Theoutputs of potentiometers 223 and 231, R sin Aand H cos i0' respectivelyare fed into height summing amplifier 237. y There 'they are added andamplified and the output, H 'cos '0' +R sin 0' is equal to H0 where H0'rcorresponds to y0 in the expression y0=y9 cos @2l-sc.,v sin 0' Theoutputs of the summing amplifiers 233 and 237 produce respectively theelectrical signals R0 and H0 when the inputs to channel 240 of computer199 are the electrical signals RB and HB and the mechanical linkage 226is at 0:40.

The summing amplifiers 233 and 237 and all other summing amplifiers ofthis embodiment are ofthe vsame basic form. These summing amplifiers(e.g. 233) have two inputs, equivalent circuits of which are shown inFig. 11. Input one to the summing amplifiers is represented by E1, R1,and input two is represented by E2, R2, Where E1, E2, and R1, R2, areopen circuit output voltages and output impedances respectively. Theimpedances R1 and R2 are made equal and the voltage across R3, thesumming amplifier input impedance is therefore equal to k(E1-{E2) bysuper position. Here k is a factor less than unity. Thus, the summingamplifier connected to R3 (e.g. summing amplifier 237) has a singleinput voltage that is proportional to the sum of its original two inputvoltages. The requirement on the summing amplifier is that its gain beconstant. The value of its gain and bandwidth depend upon designcharacteristics of the circuits with which it is employed and are wellWithin the state of existing art. (The summing amplifiers of generalpurpose computers require very high gain and the concomitant lowbandpass, for their operation.)

As previously explained, each image spot is produced twice for eachcycle of rotation of screen 56, when 0=6, and again when 0=0+180. Theoperation of the computer 199 for 0=0 was described above. When 0=0+180the radius signal -RC produced by ampli- 1S linkage 226 is common forall the driven potentiometers A223, etc. of rotation computer 199.

Refer now to Figs. A and 10B which show in more detail the linkagebetween servo motor 242 and elements 223, 224, 230 and 231. The servomotor 242, the sine and cosine potentiometers 223, 224, 2311, 231, andmechanical linkage elements 226a to 226d are all mounted fier 251 (Fig.3) is impressed on radius amplifier 222 l sinc'e reverse gate 250 is nowactivated and the inverted signal is utilized. The height amplifier 229receives the signal HC again. The signals RC and H-c correspond to thecoordinates (-x ye), and produce a reverted image of (x5, ya) (see Fig.2B). This reversion is required to place the second image in the sameposition in the display chamber 70 as the first. The outputs of all thepotentiometers 223, 224, 230 and 231 now correspond to 0-l-l80; so thatnow R0=R cos (a4-180) -H sin (H4-180) and H0=H cos (0-1-180) -R sin(0-1-180). (See Fig. 2B.) R0 now corresponds to x0 and H0 corresponds toy0', -R to x0 and H to ye; so that reversion and rotation are bothaffected.

Channel 240' of rotation computer 199 is similar in function to that ofchannel 240 except of course that it receives different electrical inputsignals and its output drives another electron gun 236 (Fig. l) of thecathode ray Itube 51 within generescope 50. The potentiometers 223',224', 230', and 231 of channel 246' are driven by the same mechanicallinkage 226. However, the gates 249 and 250' therein receiveintelligence signals that originate in moving film signal source 149.

There are three inputs into a given channel (e.g. 240) of computer 199.They are radius and height electrical signals, RB and HB and theelectrical signal indicative of the angle 0' of screen 56. Theelectrical signal inputs indicative of the angle 0 to each channel ofthe computer 199 will now be described in connection with their origin.The bearing angle 0 of screen 56 is introduced through the mechanicallinkage 226 and its ultimate control originates in generescope 50. Therea servo generators137 is mechanically driven, as previously described,in synchronisrn with the screen 56. Generator 137 in turn Vdrives servomotor 242 through one of the outputs of servo amplifier 243 so that theangular rotation of screen 56 is reproduced in the mechanical linkage226. This on a common support plate 247. The servo motor 242 drives ashaft 226a on which is rigidly mounted a gear 226b. This gear 226bengages gears 226e and 226:! and through their shafts 226e and 2261cdrive' the sine and cosine potentiometers 223, 224, and 230, 231yrespectively. The shaft 226a and the base'plate 247 are shown broken ofiat the left in Figs. 10A and 10B indicating that they extend further andrespectively drive and support other groups of potentiometers. Theseother potentiometers are not shown in Figs. 10A and 10B, but arerepresented in' Fig. 3 by all other potentiometers 223', 224', 230', 231as well as 60 and 61 that are driven by mechanical linkage 226. Thismechanical linkage 226 comprises in part the mechanical elements 226aand 226f that transmit the motion from the servo motor '242 to thepotentiomete'rs.

While the rotation computer 199 uses analog techniques involvingmultiplication and summing, the limited nature of the operations and theconditions under which they are performed inherently permit largebandwidths for short pulses and high data rates. Multiplication isaffected -by the application of electrical signals to a potentiometerand the picking ofic of a portion of those signals by the mechanicalmotion of a Wiper arm (see Figs. 9A and 9B). This action does not limitthe rate at which the electrical output signals as well as theelectrical input signals may change.

Refer again to the overall block diagram, Fig. 3. A moving film source149, a slight'modication of moving film signal source disclosed incopending application S.N. #708,474, generates signals for the displayof three dimensional images of predetermined scenes. These signals aretransmitted to source amplifiers 19S comprising radius, height, andintensity preamplifiers 266, 267, and 26S respectively. Sourceamplifiers 198 send radius and height signals to channel 240 of rotationcomputer 199. The radius and height signals are processed for effectiverotation, by channel 240 of computer 149 and with an intensity signalfrom source amplifiers 198 are fed' into channel 245 of the drivingcircuits 46 whence they are fed into a second electron gun 236 (seeFig. 1) in cathode ray tube 51 of generescope 50.

Referring now to Fig. l2, there is shown a film signal source 149 whichis an apparatus similar to multichannel magnetic tape reproducers ormultichannel sound film re-` producers. It, however, produces severalelectrical signals from a record on a photographic film strip 150, whichproduce in generescope 5G (of Fig. 3) three dimensional scenes. Themoving film signal source of this application is similar to that ofcopendng application S.N. #708,474 except that it hasonly one compositetransducer 158, and each field recorded on film 15d defines adiametrical section rather than a radial section.

The moving film signal Asource 149 may be operated in either of threeways. In the first way, the lm 150 moves from the storage reel 153 overroller 149a, through the optical transducer 158, over a series ofrollers 14% to 149i, over roller 149]', and finally to take up reel 154.In this case, a temporal sequence of three dimensional scenes will beproduced in generescope 5t) so that motion may be exhibited. In thesecond mode of operation, a continuous loop of flrn 150 moves fromroller 149a to roller 149i as previously described, but continues overrollers 149k to 149p whence it returns to roller'` 149a to make the loopcomplete. In this second mode, a motionless three dimensional scene maybe produced in generescope 50. In a third Way, a continuous loop ofkfilm isv 'memset again used to produce three dimensional imagesexhibiting cyclic motion as shall be described below.

The movement of film strip 150 (shown in detail in Fig. 13A) in any caseis driven by all sprocket wheels 151, that engage film 150 for positivelinkage at sprocket holes 150a. These sprockets wheels 151 are alllinked mechanically to servo motor 152, which in turn in controlled byservo generator 221 through the second output of servo amplifier 243(Fig. 3). Servo amplifier 243 is coupled to servo generator 137 which ison generescope 50 as previously described. Thus, iilm 150 is driven sothat its motion is continuous, and synchronized with the motion of thescreen 56, of generescope 50 (Fig. 3). The optical transducer 158transforms the data recorded on film 150 into electrical signals thatare carried ultimately to one electron gun of cathode ray tube 51. Adetailed description of the operation of transducer 158 follows thedescription of the record on film 150.

Refer now to Fig. 13A. This broad view of iilmY 150 shows that it isdivided into three longitudinal tracks; radius track 155, height track156, and intensity track 157. These three tracks 155, 156, and 157 storerespectively, substantially, the range, height, and intensity data forthe sections to be displayed. In radius track 155, a transverse distanceacross the clear portion of that track is a measure of the recordedvalue of the radius data for a section to be displayed. For height track156, the transverse distance across the clear portion of that track isagain a measure of the recorded value of the height data. However, inintensity track 157, only the trans verse distance across the clearportion above cut oli` level 150b is a measure of the recorded value ofthe intensity data. Cut off level 150b corresponds to the cut olfvoltage level of the electron gun 236' of cathode ray tube 51 of thegenerescope 50 (see Fig. 3) so that the recorded value of intensitycorresponds to the brightness of the display.

A single transverse line across the film 150, at Z1, intersects theradius track 155 at 171, height track 156 at 172 and intensity track 157at 173, to mark ofi respectively some given values of radius, height,and intensity, of a point to be displayed. The three values at 171, 172,and 173 determine the three coordinates (r, h, i) of a point P in adisplay section. That is, any three collinear transverse distances, aspreviously defined, across the three tracks refer to a common point in aradial display section. The lentgh of film 15() from Zoo to Zn,hereinafter called a field, contains a record of a diametrical sectionof a scene 265 shown in Fig. 13B as it would appear on the face ofcathode ray tube 51.

Refer again to Fig. l2 in conjunction with Figs. 12A and 12B. Aspreviously stated, film 150 moves through optical transducer 158 in themoving film source 149 where the data recorded on the film 150 istransformed into electrical signals. In the cross sectional view ofoptical transducer 158A (Fig. 12A) it may be seen that light from lamp161, a constant light source, by passing through lenses 162b and 163b,limited by stops 164 and 165, is brought to a focus at slit 160b in mask159. It passes through film 150 behind mask 159 to lens 166b whichfocuses the transmitted light on the photomultiplier tube 167b.

The mask 159 with lm 150 behind it is shown isolated in Fig. 12B. Thethree slits 160a, 160b, and 160C in mask 159 are long narrow aperturesthat lie astride radius track 155, height track 156, and intensity track157 resepctively. The are collinear and traverse the film 150.

There are three single track transducers side by side that compriseoptical transducers 158 shown in Fig. 12A.

They are marked 143:1, 143b, 143e, and transform the recorded data ofradius, height, and intensity tracks 155,*u 156, and 157 respectivelyinto electrical. signals, RA, HA, I'A, respectively. The path of lightto be traced through.

height track transducer 143i: in'this view corresponds to the path oflight described labove in connection with' portion of height track 156behind slit 160b as is the electrical signal, H'A, that the luminousflux generates. Light stops 164 and 165 are common to all three tracktransducers 143a to 143e and help define and limit the light beam:Partitions 158e, 158:1, 158e, and 158)L also prevent stray light pathsand subsequent cross talk between channels.

The radius and intensity track transducers 143a vand 143e operate in thesame way. Since the -slits 160a,

l'160b, 160e in mask 159 are collinear, andthe clear portions of thethree tracks on the same transverse line across film 150 give the valuesof the coordinates (r, h, i) of a point in a sectional view of thedisplay, then the three electrical signals, R'A, H'A, I'A, respectivelygenerated at the same time also deiine the point.

It will be appreciated that each section 265 (Fig. 13B) requires acertain amount of time, 1- (the display period increment) for itspresentation. During this period, the rear projection screen 56fingenerescope 50 rotates through an angle A0', the angular definition ofthe unified scene. The number of sectional views displayed in half arevolution of screen 56 is, of course, ISO/A0'. In a half revolution ofscreen 56 the complete volume of the three dimensional irnagespace ofgenerescope is swept out and consequently a complete three-dimensionalimage is formed which is comprised of diametrical sections. In the nexthalf of revolution, the same three dimensional image, is again swept outfor all viewers of the display are to see the same thing. Thus, vtheISO/A0' sectional views include all the sections displayed for a singlesolid image, and there must be at least 180/A0 lengths of film Z0 to Znor fields which comprise a division. For the display of a single solidimage this number of fields, 180/A0 or a division may be suiiicient.Loop operation of moving fihn signal source 149 as was previouslydescribed can be em ployed and the loop may have a division of only 180/A6' fields; the first and last elds being connected. In the second halfof revolution of screen 56 the loop is played over again for a secondtime. The same division is used twice for every cycle of screen 56.

Y For scenesdepicting motion, film 150 is played through the transducer158 only once, and the film strip then has a division of 180/ A0 fieldsfor the display of a single solid image corresponding to half arevolution of screen 56. The film strip has anotherdivision of ISO/A0fields of the sections in the same sequence for the second half ofrevolution of screen 56. The record then comprises a series of suchdouble divisions or blocs to depict motion in three dimensional scenes.

The motion of film 150 in moving film signal source 149 (Fig. 3B)produces the radius, height, and intensity signals, RA, H'A, and I'Arespectivelyof sectional views of unified scenes. I'hese RA, HA, and IAsignals are amplified in the radius preampliiier 266 (Fig. 3) and in theheight preamplifier 267 where a D C. level of zero volts is insertedmidway between the signal extremes by well known methods. Thus, anoutput signal of zero volts refers to a positional (radius or height, orthe equivalent x, y) value of zero (see Fig. 2) and a positive signalrefers proportionally to a positive position, while a negative signalrefers proportionally to a negative position. The

bipolar balanced R, radius, and H, height, signals fromradiuspreamplifier, 266 and height preamplifier 267 are fed into radiusamplifier 222A and height'ampliier 229 of channel 240' of therotation1computer`l99. In channel. ,1- n 2 40'the- R and H signals areprocessed as previously de l scribed in connection with channel 240 ofcomputer 199

